Electric heater



Feb. 27, 1934. G, HOFFMAN 1,948,759

ELECTRIC HEATER Filed June 13, 1931 Patented Feb. 27, 1934 UNITED STATES ELECTRIC HEATER George D. Hoffman,

Pasadena, Calif, assignor,

by mesne assignments, to Thermador Electrical- Manufacturing Company,

Los Angeles, Calif., a

corporation of California Application June 13, 1931. Serial No. 544,072

19 Claims.

The present invention relates to electric room heaters adapted to be mounted in, on or near the wall of a room and having circulating means by which air from the room is caused to flow into the heater at one side and heated air is discharged into the room from the same side of the heater. Its object is to provide an improved heater of this type having novel characteristics of structure, arrangement and operation by which eflicient results in operation and economy of manufacture and installation are secured. The invention comprises the novel features hereinafter described and particularly pointed out in the claims.

In the drawing- Fig. 1 is a front elevation of a heater embodying this invention, with exterior parts broken away to show the interior;

Fig. 2 is a sectional view of the heater taken on line 2-2 of Fig. 1 and a fragmentary vertical section of a wall showing the heater as installed in the wall;

Fig. 3 is a fragmentary sectional view on a larger scale showing a detail of construction;

Fig. 4 is a similar enlarged sectional view taken on line 4-4 of Fig. 1 showing another detail;

Fig. 5 is a fragmentary rear elevation of the front plate or grille showing the lower portion thereof;

Fig. 6 is a section taken on line 6--6 of Fig. 5;

Fig. 7 is a fragmentary perspective view showing details of the means for mounting the heating elements;

Fig. 8 shows in elevation that one of the coil supporting members to which the ends of the heating coils are held, together with the heating coils and a fragmentary section of the shell on which the support is mounted;

Fig. 9 is a detail sectional view taken on line 9-9 of Fig. 8;

Fig. 10 is a perspective view of the air propeller by which flow of air into, through and out of the heater is induced;

Fig. 11 is a diagram of the electrical equipment of the heater.

Like reference characters designate the same parts wherever they occur in all the figures.

The wall indicated in Fig. 2 represents a partition wall between rooms in a frame structure, constructed of studs 1 and 2, and sheathings 3 and 4 of any suitable material. But it typifies a wall of any construction, whether a partition or outer wall of a building.

The form of heater here shown is particularly designed to be set into a space between the studs of a wall through an opening in the inside face of the wall, or into a recess otherwise provided in a masonry wall. To that end it comprises a front plate or grille 5, heating means 6, '7, an air impeller 8 driven by an electric motor 9, a reversing air deflector or reflector 10, and a frame 11. These parts are combined with an open sided box 12 which is inserted into the wall and encloses a dead air space enveloping the deflector 10. Such box is made of non-inflammable material, preferably pressed steel, with side walls and a rear wall, but no front wall, and an outward flange 13 at the forward edge of its side walls. Its width is enough less than the standard spacing between studs of a frame wall to permit placement in the wall without touching the stud on either side, and of a length or vertical height great enough to receive, not only the deflector bowl 10 of the heater, but also a block 14 carrying the switches by which the electric circuits of the heater are controller. When made of sheet metal it is constructed without openings in its walls but with offset circular areas 15, similar to the so-called knock-outs of junction and outlet boxesused in the electrical art, at convenient locations, any of which may be broken out to leave a hole 16 for passage of an electric cable 1'7. The box 12 may be of any desired outline but is preferably rectangular.

The air deflector 10 is a bowl-like member, made preferably of sheet metal, pressed or spun 5 into shape, of circular outline, having flaring or conical side walls joined to the bottom or rear wall on a smooth curve of sufllciently large radius.

It has an outturned flange 19 on the forward rim of its side walls.

The grille 5 or perforated front plate is associated with an interior annular partition 20, dividing the inlet space, in which the heating means 6 and motor 9 are located, from the outer annular discharge space 21. Conveniently the grille is 5 made as a casting and the partition 20 as an integral, annular rib on the inner side of the grille concentric with the circumference thereof. Pref erably also it is bulged outward in order to provide sufficient depth in the front to rear dimension of the heater, and is formed with a peripheral flange 22. It is made with a circular series of holes 23 opening into the discharge space, and more numerous and smaller holes opening into the central space within the partition 20. The outer series of holes 23 is interrupted at the lower side of the grille, leaving a blank wall 511 there, as shown in Fig. 1; and back of such blank wall is a bafiiing or deflecting wall 5b which is of inwardly or rearwardly bulged and curving 11o formation. The purpose and effect of these walls is to prevent outflow of heated air at the lower part of the heater so as to avoid interference by the outflowing air with the air which passes upward from the lower level adjacent to the heater into the central group of holes. The baffling wall is so formed as to obtain this effect in the fullest possible manner, having a convex and relatively abrupt curvature at the side which is approached by the fan blades and tangential air currents (being the right hand side in Figs. 5 and 6), and a concave and gradual curvature outwardly on the receding side.

The casing of motor 9 is formed with a central boss 24 on its forward end which projects through a central hole in the grille and has an outwardly accessible oil hole at 25. It also has two posts 26, one at either side of the boss 24, which extend to the grille and receive screws 27 whereby the motor is made fast to the grille and supported. Surrounding the motor casing is a sleeve or shell 28 open at both ends, and having at its rear end two or more inwardly directed lugs 29, which overlap the rear end of the'motor casing and are screwed thereto, whereby the shell is made fast and centered.

Such shell is slightly larger in diameter than the motor casing and is mounted coaxially so that it encloses an annular air space through which air flows when the fan or impeller is in operation. It also serves as a base for the heating units 6 and 7, and as a shield against direct impingement on the motor housing of radiant heat from the heating elements. It is provided at intervals around its circumference with loops or sockets 30 in each of which is held the foot 31 of a radially extending bar 32.

Each such bar and a backing strip 33, which are secured together by rivets 34, cooperate to clamp and hold an intermediate plate 35 of insulating material, preferably mica, which extends to either side of the bar and is pierced with holes 36 to receive the heating units, the latter being helical coils of resistance wire extending in a spiral course a number of times around the shell and through a different one of the holes in each of the turns of the spiral. The holes are of a size near enough to that of the wire to receive the wire freely and hold it without excessive looseness. To facilitate entrance of the wire into them, the plate is cut so as to form slits 36a leading from each hole to the nearest edge of the plate. By springing the material of the plate apart at such slits, an entrance passage is provided by which the wire may be slid laterally into the adjacent hole, a convenient and rapid mode of assemblage which avoids the necessity of threading a long length of wire endwise through the hole. These plates 35 with their supporting and securing bars constitute holders for the heating units. Intermediate spacers 37, being similar plates of insulating material, are placed on the heating unit coils between the previously described holders 32, 35.

It will be appreciated that the shell 28 serves the triple purpose of supporting the heating units, shielding the motor from the radiant heat of the units, and providing a channel for cool air from the outer space to flow in direct contact with the motor and its field coils and armature. In order to serve these functions most eiiiciently and economically, the shell is made of opaque, refractory, tough material, preferably steel, and as a cup pressed or drawn from sheet steel and having its bottom punched out in a fashion and releasing the heating elements, made ofv thin sheet steel, U-shaped in cross section and secured by compression on the edges of the plate. While such bindings may be continuous from the inner to the outer ends of the supporting plate, they are preferably made in two or more parts separated from each other by a sufficiently wide gap to avoid being a means of short circuiting adjacent turns of the heating unit coils.

While the details of structure and material last described are important, and claimed as elements of the invention, it is to be understood that the range of equivalents which I claim for the invention include other sheet metals than steel for the parts described as metallic, and other materials than steel and mica for the sup porting and insulating parts of this structure.

This mode of mounting the heating elements causes them to surround the motor and places them in what may be considered, for the convenience of this description, as the same zone of the heater with the motor. The zone referred to contains also the partition 20, and the entire motor and heater unit assemblage is substantially contained within the space embraced by this partition.

The motor shaft protrudes from the rear end of the motor casing, and on its end is affixed the fan or impeller 8. The vanes or blades 39 of the latter are preferably arranged in planes radial to the axis without any, or at most very little, inclination to the path in which they travel, so that the flow which they impart to the air is in the plane of the fan, with a large radial component due to centrifugal force. As a convenient structural measure, the impeller is preferably made out of a flat disk of suitable material, as thick sheet aluminum, or other sheet metal, from which at regular intervals sectors are punched out, leaving radial spokes 40 with a rectangular strip of metal integrally attached to the corresponding side of each. These attached metal strips are bent up perpendicular to the plane of the disk, forming the vanes or blades 39 above described. The center of the disk is provided with a hub 41 having a bore adapted to receive the motor shaft and in the side of which is a set screw 42 for clamping it to the shaft. Other equivalent means of well known character may of course be used instead of the set screw for this purpose, such as a lock nut on the end of the shaft. The impeller is set close to the inwardly rear part 18 of the bowl 10, and spaced at an appreciable distance from the heating elements, this arrangement having been conceived, and proved by experience, to be efficient in promoting smooth and continuous air flow, with a maximum directness of outflow.

The main parts of the heater structure are assembled and connected in the following manner. First, the deflecting bowl and grille are placed with their flanges face to face and secured by two or more screws 43 and securing nuts thereon, as shown by Fig. i. The box 12 is set into the recess provided for its reception in the wall and made fast or not as may be demanded by the circumstances of installation. The frame 11 is placed against the wall and secured to the outturned flange or flanges of the box by bolts .4 and nuts thereon, as shown in Fig. 3. Finally the deflector and grille assemblage is applied to the frame so that the deflector enters the opening in the latter, and studs 45, which protrude from the frame, pass through alined holes in the flanges 19 and 22. Cap nuts 46 are screwed on the protruding threaded ends of these studs. Said studs are equally spaced around the circumference of the heater, projecting from bosses 4'7 on the frame which provide abutments against which the deflector and grille assemblage is clamped by the cap nuts. Intermediate abutments are provided at the points 47 indicated in Fig. 1, by other bosses on the frame which have no protruding studs. It will be noted that the flange 22 of the grille extends beyond the circumference of the flange 19 of the deflector, and that it has a rearwardly inclined lip at the edge. Such lip embraces the rim of the deflector flange and gives a desirable finished appearance. These abutments maintain a separation and a cooling air space between that part of the heater structure which supports the heating elements and the cooperating structure which secures the heater to the wall, preventing conduction of heat from one part to the other except for the small amount capable of being conducted through the bosses.

The frame 11 has an outline corresponding to that of the box 12, and is enough larger in both dimensions to overlap the edges of the wall recess in which the box is inserted. It has a central circular opening in its interior for reception of the heater proper, the lower part of which is extended with a rectangular outline to receive a corresponding extension 48 of the grille, to the back of which the switch block 14 is secured and on the front of which a name plate 49 is mounted.

The heating elements 6 and '7 and the motor are connected in separate electric circuits, controlled by switches 50, 51 and 52, which are mounted in the block 14, which is made of insulating material, so that their operating handles or levers protrude through slots in the name plate. Switch 50 is of the single pole type, and switches 51 and 52 of the double pole type. All are preferably snap switches of any suitable character, various types of which are known and available in the market, connected in parallel circuits so as to compel operation of the motor when either heater switch is closed. One lead conductor L of the power circuit is connected directly to one pole of switch 51 at the point 53, and to one pole of each of the other switches through a conducting bar 54. The other conductor, L, of the power circuit is connected to the other pole of switch 51 at 55, and with the second pole of switch 52 at point 56 through a conductor 5'7. The contact 58 of switch 51 is connected by a conductor 59 with one terminal of coil 6. Contact 60 of switch 52 is connected by a conductor 61 with one terminal of heating element '7. The opposite terminals of both elements are connected together by a fusible bar 62 from which a conductor 63 leads to the contact 64 of switch 52, the latter being connected with contact 65 of switch 51 through a conducting bar 66. One terminal of the motor circuit is connected with the contacts 64 and 65, and bar 66, by a conductor 6'7, and through the bar with one side of switch 50. The other terminal of the motor is connected through the conductor 68 with the conductor L of the power line.

It will be apparent that when the switch 50 alone is closed, the motor will be set running but neither heating circuit will be closed, thus circulating the air at room temperature. If switch 51 is closed, the heating element 6 and the motor are simultaneously set in operation, causing the air in circulation to be heated. When switch 52 is closed, the element '7 and motor are simultaneously put in operation; while if both switches 51 and 52 are closed at the same time both heating elements and the motor are operated. By making the heating elements 6 and 7 of different capacities, three different degrees of heating effect may be obtained. In any event, it is normally impossible to turn on the heat without at the'same time causing the fan to run. This prevents overheating of the elements, for the rapid flow past them of air at the room temperature, induced by the fan, carries away heat from the elements so fast as to keep their temperature below that of red heat. But the fan may be run for cooling purposes without turning on the heat.

Thermostatic control may be applied to maintain an even temperature in the room, and I have here shown a suitable means for that purpose in combination with the heater before described. Such means comprises a thermostatic switch 50a mounted on the outside of the front plate and connected in the lead L of the power circuit in advance of the manual switches, as shown in Fig. 10. The heat responsive element of such thermostatic switch may be of any character suitable for the purpose, such as a curved bimetallic barfa diaphragm or bellows type, etc., all of which are well known in the heating art and require no specific description here. By being placed in the location described, the thermostatic switch is directly affected by the air temperature in the room, and is shielded by the blank wall and bafile member of the grille from the direct influence of the heated air discharge. However, the thermostatic switch may be located at any other point more or less remote from the heater, wherever convenient.

It is only when some accidental condition prevents the motor from running that danger of overheating the elements could arise. To safeguard against this possibility is the reason for the fusible connection 62 through which both elements are connected to one of the lead conductors. Such connection is exposed to the radiant heat of the elements and the air heated thereby, and it is designed to melt, breaking the circuit, when the heat so generated reaches the degree prescribed as the safe limit.

One terminal of each of the elements 6 and 7 is mounted in the uppermost hole, one at each side of the supporting bar, of one of the insulating supports 35 at the under side of the heater, and such ends are secured by nuts 69 with the conductors 59 and 61, respectively. The elements are thence led, each in a volute curve around the motor through the innermost holes of each of the other supporting blades in turn, then successively through the middle and outermost holes of the several supports until all the holes are occupied,

when the outermost terminals are secured to the The characteristics herein disclosed provide a maximum of desired heating effect with safety against overheating and a minimum of bulk, and minimum over all dimensions, particularly the front to rear dimension. The box 12, by enclosing the deflecting member, with its rear wall separated from the rear wall of the latter, provides an eifecdve air insulation against conduction of heat into the interior space of the wall, keeping the temperature at the outside of the box well below the permissible limit allowed by the fire underwriters.

The necessity of a space between the rear walls of t .e deflecting member and of the enclosing box requires the grille to be bulged outward at the front of the heater, as previously mentioned; but the arrangement of the heating elements surrounding the motor enables the front to rear dimension of the heater and its protrusion from the face of the wall to be a minimum consistent with the necessary heating effect. This arrangement permits an appreciable space to be provided between the heating elements and the fan, which in turn enables the streams of air divided in passing the coils of the units to merge together in a smooth flow before reaching the fan. This is a factor which enhances the smoothness of flow of the annular air stream which is discharged by the fan, changed in direction by the deflector l0, and emitted from the peripheral row of openings in the grille which lead from the outer chamber 21.

The box 12 may be made of the same dimensions as the frame or front plate 11, and the heater thereby adapted for use as a portable heater to be set on the floor or on a low support anywhere, or mounted entirely outside of the wall surface.

The switches may be located otherwise than within the box 12, for the purposes of remote control, and a cable containing the conductors 59, 61, 63, 68 and 67, or their equivalents, led to the heater from switches located at any remote point. This permits of a modification in design by shortening the vertical dimension, to be used as a portable heater or mounted in, or externally on, a wall.

What I claim and desire to secure by Letters Patent is:

1. An electric heater comprising a grille, an annular partition projecting rearwardly from said grille between the center and the hery thereof, a deflector having a rear wall spaced apart from said grille and from the rear end of said partition, and having also forwardly extending side walls contiguous at their forward edges to the periphery of the grille, a motor and an electric heating element surrounding the motor, both located in the space surrounded by said partition, and an air impeller driven by said motor and located adjacent to the rear wall of the deflector.

2. An electric heater comprising front and rear members contiguous to one another peripherally and offset away from one another in their central parts, one of said members being a grille haying peripheral and central openings and a rearwardly directed annular partition being associated with said grille between the central and peripheral openings, and the other of sa d members being substantially imperforate, elec "ic heating means located in the space surrounded by said partition and air impelling means arranged to induce air flow through the central part of the grille past i said heating means and, in cooperation with the deflecting member, to expel the air through the peripheral openings in the grille.

3. An electric heater comprising a deflector having a rear wall with a forwardly offset central area and encircling side walls projecting forwardly from the rear wall and joined therewith on a smooth curvature, a rotatable air impeller arranged to rotate in a plane parallel to said rear wall and located close to the forwardly offset area thereof, an annular partition substantially coaxial with said deflector embracing a central inlet space of a diameter approximating that of the impeller and dividing such space from an annular outer discharge space, and electric heating means located in the said central space.

4. An electric heater comprising electric heating means, a partition surrounding said heating means and enclosing an inlet space open at the forward end, an air impeller at the rear of said space adapted to induce flow of air past the heating means, a deflector in rear of the impeller having surrounding side walls of larger diameter than the impeller extending forwardly of the rear end of said partition, to form in cooperation with the partition an annular discharge chamber through which the flowing air is discharged in a direction opposite to the flow through the inlet; and means for supporting the before named parts in the relationship set forth.

5. An electric heater comprising a grille and a deflector peripherally connected together and centrally offset away from one another, electric heating means, an electric motor and an air impeller mounted in the space between the grille and deflector and arranged to induce inward flow of air centrally of the grille past the heating means and positively discharge air from the peripheral part of the grille, and an outer box enclosing the deflector and confining an insulating body of air which envelops the deflector.

6. A heater as set forth in claim comprising also a frame, means for securing said box and frame together, and separate means for securing the grille and deflector assemblage to the frame.

7. An electric heater comprising a grille, a defiector, air heating and circulating means between the grille and deflector, a box enveloping the deflector, and a frame; connecting means for securing the grille and deflector peripherally together in one assemblage, separate connecting means for securing the box and frame together, and other connecting means for securing the first assemblage to the frame with the deflector protruding through a central opening of the frame into said box.

8. An electric heater comprising a grille, a deflector, air heating and circulating means between the grille and deflector, a box enveloping the deflector, and a frame; connecting means for 1 securing the grille and deflector peripherally together in one assemblage, said grille having a peripheral flange, separate connecting means for securing the box and frame together, and other connecting means for securing the first assem I 1' blage to the frame with the deflector protruding through a central opening of the frame into said box, the last named means comprising studs protruding from the frame through said peripheral flange, and nuts screwed on the protruding ends 1? of said studs.

9. An electric heater comprising a grille, a deflector, air heating and circulating means between the grille and deflector, a box enveloping the deflector, and a frame; connecting means for securing the grille and deflector peripherally together in one assemblage, said deflector having an outstanding peripheral flange, separate connecting means for securing the box and frame together, and other connecting means for securing the grille and deflector assemblage to the frame with the deflector protruding through a central opening of the frame into said box, the last named means comprising studs protruding from the frame through the peripheral flange of the deflector, and nuts screwed on the protruding ends of said studs.

10. In an electric heater of the character set forth, a frame member having a central opening and studs protruding from one face thereof, a dished deflector having a peripheral flange, a grille also having a peripheral flange, said flanges being of diameters larger than the central opening in the frame, overlapping said studs and having alined openings through which the studs project, and nuts screwed on the protruding ends of the studs.

11. In an electric heater of the character set forth, a frame member having a central opening and studs protruding from one face at intervals around such opening, a dished deflector having a peripheral flange, a grille also having a peripheral flange, said flanges being of larger diameter than the said central opening, and the flange of the grille being extended beyond the flange of the deflector and embracing the latter, said flanges overlapping the studs and having alined openings through which the studs project, and nuts screwed. on the protruding ends of the studs.

12. In an electric heater of the character set forth, a frame member having a central opening and studs protruding from one face thereof, a dished deflector having a peripheral flange, a grille also having a peripheral flange, said flanges being of substantially equal diameters larger than the central opening in the frame, overlapping said studs and having alined openings through which the studs project, and nuts screwed on the protruding ends of the studs, and other fastening means independently connecting said flanges together in a unit assemblage.

13. An electric motor and heating element assemblage comprising plates of insulating material mounted externally of the motor casing at intervals in a series surrounding the casing, and extending substantially radially thereto, said plates having apertures, and a helical resistance element passing through said apertures in a course surrounding the motor.

14. An electric motor and heating element assemblage comprising plates of flexible insulating material mounted externally of the motor casing at intervals in a series surrounding the casing and extending substantially radial thereto, and a heating element of helically coiled resistance wire, said plates having holes of suitable size for receiving the resistance wire and having slits extending from said holes to an adjacent edge of the plate, adapted to be opened for admission of the resistance wire into the holes, said holes being so arranged in the several plates that the resistance wire is supported in a course surrounding the motor.

15. An electric motor and heating element assemblage comprising a motor having a casing, a tubular shell surrounding said casing and secured thereto and having sockets spaced circumferentially, outstanding bars mounted in said sockets, apertured plates of insulating material secured to said bars, and an electrical resistance element passing through said apertures in a course encircling the tubular shell.

16. An electric motor and heating element assemblage comprising insulating plates surrounding the motor and arranged in intersecting planes substantially coincident with the motor axis and heating elements surrounding the motor, passing through said plates one after another, and being supported by the plates.

17. In an electric heater, an electric motor, an electric heating element spirally surrounding said motor, insulating means supporting the coils of said heating element and holding them apart from one another and from the motor, an annular partition surrounding the heating element, a fan on the shaft of the motor arranged to indue flow of air past said heating element through the space enclosed by the partition.

18. In an electric heater, an electric motor, an electric heating element spirally surrounding said motor, insulating means supporting the coils of said heating element and holding them apart from one another and from the motor, an annular partition surrounding the heating element, a fan on the shaft of the motor arranged to induce flow of air past said heating element through the space enclosed by the partition, and deflecting means partially embracing said partition and arranged to cause reversal of the induced air flow.

19. In an electric heater, an electric motor, heating element supports arranged in a series surrounding said motor, an electric heating element carried by said supports in a course surrounding the motor, an annular partition surrounding said heating element, a fan on the motor shaft arranged to induce flow of air past the heating element through the space enclosed by the partition, and a deflector extending across one end of such space, at a distance from the adjacent end of the annular partition, and having 11 side walls embracing the adjacent part of the partition and separated therefrom by an annular space, whereby to cause reversal of the air flow.

GEORGE D. HOFFMAN. 

